Stanford Encyclopedia of Philosophy

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NOV
8
2001

Causation in the Law

The basic questions dealt with in this entry are: (i) whether and to
what extent causation in legal contexts differs from causation outside
the law, for example in science or everyday life, and (ii) what are the
appropriate criteria in law for deciding whether one action or event
has caused another, (generally harmful) event. The importance of these
questions is that responsibility in law very often depends on showing
that a specific action or event or state of affairs has caused specific
harm or loss to another. Are the criteria adopted in deciding these
causal issues both objective and properly attuned to the function of
fixing responsibility?

The entry covers the nature and functions of causation, the relation
between causation and legal responsibility, and the criteria for the
existence of causal connection in law. The last topic is treated in two
parts: what are causally relevant conditions
(‘causes-in-fact‘) and what are the grounds for limiting
responsibility (the ‘proximate cause’ requirement).

Law is concerned with the application of causal ideas, embodied in
the language of statutes and decisions, to particular situations. This
involves, first, a conception of what a cause is outside the law. To
this a variety of answers empirical (Hume) and metaphysical (Kant )
have been given and each has its contemporary supporters.

Secondly, a theory is required of how causal notions should function
in different contexts. In the context of application the notion of
cause is a multi-purpose tool. One function, perhaps fundamental, is
forward-looking: that of specifying what will happen and by what stages
if certain conditions are present together. This use of cause serves to
provide recipes and make predictions. It also yields the idea of a
causal process. Another function is backward-looking and explanatory:
that of showing which earlier conditions best account for some later
event or state of affairs. A third function is attributive: that of
fixing the extent of responsibility of agents for the outcomes that
follow on their agency or intervention in the world.

For the first of these purposes the emphasis falls on a cause as
consisting of the whole complex of conditions required if a certain
outcome is to follow (J.S. Mill). Even when applied to a specific
situation this involves considering what generally happens when certain
conditions are present. In the second, explanatory, context the focus
is on selecting from the whole complex the particular condition or
conditions that best explain a given outcome. The aim can be either to
explain a class of events or a particular event. In the third,
attributive, context the aim is again selective, but from a different
point of view. It is to attribute responsibility to an agent for those
outcomes that his, her or its agency serves to explain and that can
therefore plausibly be treated as part of the agency's impact on the
world. Here the purpose is to settle the extent of responsibility that
attaches to a particular human action or other event or state of
affairs. This responsibility is then attributed to an agent or,
metaphorically, to the other event or state of affairs in question
(e.g. outbreak of war, high unemployment).

In law the second and third of these functions of the notion of
cause are prominent, often in combination. Many legal inquiries are
concerned to explain how some event or state of affairs came about,
especially an untoward event such as death or a state of affairs such
as insolvency. But in law the third function is particularly salient
and controversial. Whether someone is liable to punishment or to pay
compensation or is entitled to claim compensation often depends on
showing whether the person potentially liable or entitled has caused
harm of a sort that the law seeks to avoid. For example, all systems of
law hold that a person can be guilty of homicide only if he or she has
caused another's death. All systems treat it as a more serious offence
to cause death than to attempt to do so. It is a civil wrong to cause
injury to another by negligence in driving a vehicle, but the claim is
barred or reduced if the negligent conduct of the person injured is
also a cause of the injury. An insurer is required to pay for losses
caused by an event of the type defined in the insurance policy, such as
fire or flooding, but not if the cause of the loss is something
else.

The attribution of responsibility on causal grounds is not confined
to law. Historians and moralists, for example, assess the
responsibility of agents for the outcomes, political, social, economic
or military of what they did or failed to do. Unlike lawyers, they are
concerned with responsibility for good as well as bad outcomes. But
whereas historians may aim to assess the outcome of an agent's conduct
over a period or even a lifetime, lawyers focus on the harmful outcomes
of particular actions. These uses of causation by historians, moralists
and lawyers raise the question, adumbrated by Collingwood, of whether
the attribution of responsibility requires a different conception of
cause from that employed for prediction or explanation. In the legal
theory of causation this problem is of central importance.

When rules of law attributing responsibility for harm caused are
formulated in statutes, regulations and judicial decisions, the word
‘cause’ is often used. The notion that causal connection
between agency and harm must be established is however often implied
even when the word is not used. This is true, for example, of the use
of verbs such as ‘damage’, which imply a causal relation
between an agency and the harm done. In legal contexts the possible
range of agency is not confined to human conduct, but may extend to
damage done by the agency of juristic persons, animals, inanimate
objects such as motor vehicles and inanimate forces such as fire. In
all these instances the use of the notion of cause is central to the
legal inquiry, since to establish responsibility it must be shown that
the harm was done or brought about by the agency that the law treats as
a potential basis for the existence or extent of liability.

The relationship between causing harm and legal responsibility is
however complex. The complexities concern the incidence of
responsibility, the grounds of responsibility, the
items between which causal connection must be demonstrated,
and the variety of relationships that can in some sense be
regarded as causal. So far as the incidence of responsibility
is concerned, while in law the relevant causes may be human or animal
behaviour or natural events or processes, legal responsibility attaches
in modern law only to natural persons (human beings) and juristic
persons such as states, corporations and other institutions to which
personality is ascribed in law.

As regards the grounds of responsibility it is important to
grasp that for a person to cause harm or loss to another (the term
‘harm’ will be used for short) is in law neither a
necessary nor a sufficient condition of being legally responsible for
the harm. It is not a necessary condition for two reasons. First, in
legal contexts people are often made responsible for harm caused by
other persons (e.g. the vicarious liability of employers for
employees), animals (e.g. the bite of a dangerous dog), inanimate
objects (e.g. the collapse of buildings, the impact of vehicles) or
processes (e.g. fire, subsidence). In these instances the ground of
responsibility is, from the point of view of the person held
responsible, not that he, she or it has caused harm but that they bear
the risk that some other person, animal, thing or process may cause
harm. The risk may be voluntarily assumed, as in insurance contracts,
or may be imposed by law, as in the case of employers' liability for
wrongs committed by employees in the course of their employment. Much
law is indeed concerned with the distribution of social risks. The
responsibility of the person who bears the risk may be additional or
alternative to the responsibility of the person (if any) who wrongfully
caused the harm in question. Thus, if an employer is responsible for
harm caused by his or her employee to another person the employee may
or may not also be legally responsible for that harm. In law the main
grounds of responsibility for harm are therefore (i) an agent's
personal responsibility for causing harm and (ii) a person's
responsibility arising from the fact that he, she or it bears the risk
of having to answer in legal proceedings for the harm in question.

A second reason why causing harm is not a necessary condition of
legal responsibility is that there are many contexts in which a person
is civilly or criminally responsible irrespective of whether any harm
has been caused by their conduct or that of an agency for which they
are responsible. Thus, in Anglo-American law those who trespass on
another's land or who break a contract may be civilly liable and those
who unlawfully possess firearms criminally liable though no tangible
harm is thereby caused to anyone. Both inside and outside the law many
actions are regarded as wrongful whether or not they cause tangible
harm. Moreover the imposition of penalties in civil law and of
punishments in criminal law need not bear any relation to the harm (if
any) caused by the conduct for which the penalty or punishment is
imposed.

To cause harm to another is also not a sufficient condition of legal
responsibility, even in the eyes of those, such as the early Epstein,
who would in general favour making agents strictly liable for the harm
they cause. For a person to be legally responsible for causing harm to
another requires, apart from a number of conditions relating to
jurisdiction, procedure and proof, that the conduct should be of the
sort that the law designates as unlawful (e.g. negligent driving) or as
a potential source of liability (e.g. keeping a dangerous animal). It
also requires that the purpose of the law should encompass harm of the
sort for which a remedy is sought. Thus, in some contexts only
physical, not economic or psychological harm grounds a legal remedy.
Moreover considerations of morality must not rule out liability, as
they well might if, for example, a burglar were to claim compensation
for an injury suffered while breaking a window in order to enter the
victim's house.

There is also a complication concerning the items between
which causal connection must in law be shown to exist. The inquiries
with which law is concerned relate to particular events. Did one
action, event, process or state of affairs (event for short) cause
another? The link that must be established in legal proceedings between
events is of a special type. A person's conduct or a natural event or
process can always be described in a number of different ways, but only
certain descriptions of an alleged cause are crucial in legal
proceedings. For example, if a claim for damages is brought against a
motorist for causing injury to the claimant by driving negligently,
only that description of his or her manner of driving that amounts to
negligence is capable of constituting a relevant cause. Hence ‘On
5 March at 5 p.m. Smith drove at sixty miles an hour in a built-up
area’ may be relevant while ‘;Smith drove a Mercedes’
may not be, though both correctly describe Smith's act of driving a car
on the occasion in question. In a legal context, therefore, the link to
be established must be framed in terms of a link between particular
aspects of events. The claimant in a civil action will typically argue,
for example, that the fact that Smith drove at sixty miles an hour in a
built-up area on such-and-such an occasion caused the collision that in
turn caused the victim to suffer a broken leg. Though it is
controversial whether causal connection is to be conceived as a
relation between events or facts (Davidson), in law both are relevant.
The events in issue must be identified from the point of view of the
time, place and persons involved, but the aspect of the events between
which a causal link must be shown has to be specified in such a way as
to show that it falls within the relevant legal categories, such as (in
the example given above) negligence and physical injury.

The relationship between causing harm and legal responsibility is
also complex because of the great variety of relationships
between agency and harm that can be regarded as in some sense causal,
or analogous to a causal relationship. An omission to prevent harm when
the person concerned has a legal duty to prevent it can ground legal
responsibility but would ordinarily be described as ‘not
preventing’ rather than causing the harm. Again, legal
responsibility is often imposed, in the context of interpersonal
relationships, on those who influence others by advising, encouraging,
helping, permitting, coercing, deceiving, misinforming or providing
opportunities to others that motivate or enable them to act in a way
that is harmful to themselves or to others. In some cases (coercion,
deceit) the persons held responsible would naturally be said to have
caused the persons influenced to act as they did, while in others they
would not, though the weaker interpersonal relationship is in some
respects analogous to more plainly causal relationships. Failing to
help or provide opportunities to others by advising, warning, informing
or rescuing them or supplying them with agreed goods and services are
other grounds of responsibility for negative agency that, again, are at
least analogous to causal relationships. The existence of this wide
spectrum of causal or near-causal grounds of responsibility recognised
in law and morality raises the question whether any uniform theory of
causation is capable of accounting for all of them.

The theories concerning the criteria for the existence of causal
connection in law fall into two classes. Some focus on the type of
condition that the alleged cause must constitute in relation to the
alleged consequence. Others are concerned with a specific feature that
the cause must possess in relation to the consequence in order that
causal connection may be made out. The first class of theory concerns
the identification of the causally relevant conditions of an outcome,
or, in the language of causal minimalists, ‘cause-in-fact’.
Must the cause be a necessary condition, a sufficient condition or a
necessary member of a set of conditions that are together sufficient
for the outcome? In law these terms, much discussed in the
philosophical literature, are interpreted as meaning ‘necessary
or sufficient in the particular circumstances in issue’. The
inquiry will be, for example, into what was a necessary or sufficient
to cause a particular persons' death, not what are in general the
necessary or sufficient conditions of death.

The second type of theory concerns the criteria for determining the
limits of legal responsibility for causing harm. Even supposing that
the alleged cause constitutes the right sort of condition of the
outcome (e.g. a necessary condition), responsibility cannot extend
indefinitely. The failure of a doctor to prescribe an effective
contraceptive cannot be held to be responsible for the death of the
victim of a murder committed by the child conceived as a result of the
doctor's negligence. Some consequences are ‘too remote’.
But what are the appropriate criteria of limitation?

In many legal contexts and in the view of many theorists a single
criterion is called for. It should be remembered, however, that the
search for a single criterion may be no more than a response to legal
doctrine. This sometimes requires all the limiting factors to be
brought under a single umbrella, such as ‘proximate cause’
or ‘adequate cause’ even though, underlying these phrases,
there are a number of distinct reasons for imposing limits on the
extent of responsibility. A number of expressions are used to describe
the allegedly single limiting factor, in particular ‘proximate
(adequate, direct, effective, operative, legal, responsible)’
cause in contrast with ‘remote, indirect or legally
inoperative’ causes.

Some theorists (for example Leon Green and others since the 1920's
up to Wright and Stapleton today) hold that only the issue of causally
relevant condition or cause-in-fact is genuinely causal. It alone
raises questions to which an objective, scientifically valid, answer
can be given (Becht and Miller). Even this has been questioned by
Malone, who has pointed to the incorporation of normative
considerations in the rules for proving cause-in-fact in civil law. The
second type of theory concerns questions of responsibility that would
in the view of these causal minimalists be better addressed directly
rather than by asking whether on the facts a causal relation existed
between agency and harm. One way of doing this is to ask what would be
the fairest way of distributing the relevant social risks. Another
(Posner) would be to place responsibility, especially in civil law, on
the person best placed to avoid the loss most cheaply. In practice
legislators and judges have seldom abandoned the traditional
terminology in discussing the second issue, but the proposal to do so
has been repeatedly revived.

3.1 Causally relevant conditions: ‘Cause-in-fact’

What sort of condition must be attributed to an agency for its
action or intervention (action for short) to count as causal? Opinion
is divided between those to whom the action must in the circumstances
be necessary to the outcome (a but-for condition), those to whom it
must in the circumstances form a necessary part of a complex of
conditions sufficient for the outcome (a NESS condition), and those who
would describe the required connection in a more quantitative or scalar
mode by requiring that the action be a ‘substantial factor
in’ or ‘contribute to’ the outcome.

The but-for theory, endorsed by many legal and philosophical
theorists including Mackie, has the heuristic advantage that a simple
and often reliable way of ruling out the existence of causal connection
between agency and harm is to ask whether the harm would in the
circumstances have occurred in the absence of the agency. If the harm
would have occurred in any event the agency is probably not its cause
or one of its causes. If it would not have occurred in the absence of
the agency the agency will be a causally relevant condition or, if one
endorses causal minimalism, a cause-in-fact of the harm.

There are however cases in which the but-for test is difficult to
reconcile with our intuitive judgements of responsibility. These
concern two types of case in particular, those of over-determination
and of joint determination. If two huntsmen independently but
simultaneously shoot and kill a third person, or two contractors
independently fail to deliver essential building supplies on time, it
is intuitively clear that each should be held responsible for the death
or building delay. Yet the but-for test seems to yield the conclusion
that neither has caused the harm. Again, in interpersonal relationships
it is often the case that advice etc. can be regarded as contributing
to a person's decision without its being shown that the person would
not have acted as they did apart from the advice. Many reasons bear on
the decisions we make. Sometimes it is not possible to be sure that in
the absence of one of them the decision would have been different. We
know only that to the person reaching the decision the reasons taken
into account were jointly sufficient to induce him, her or it to decide
as he or she did.

In reply it is argued (Mackie) that in these cases all the agencies
that are singly or jointly sufficient for the outcome together
constitute its cause. But in law this does not solve the problem
because, unless the agents are acting in concert, the responsibility of
each agency has to be independently established. This can be done
either by an appeal to intuitive notions of responsibility or by
recourse to an alternative ground of responsibility based on risk. On
the alternative view an agency that provides an independently or
jointly sufficient condition of harm bears the risk that that harm will
eventuate even if it would in the circumstances have come about in any
event.

Some of those who reject this approach (e.g. Hart and Honoré,
Wright) have recourse to a theory based on J.S.Mill's notion of a
jointly sufficient set of conditions. The theory also draws on Mackie's
idea, in the context of causal generalisations, of an INUS condition
(insufficient but non-redundant part of an unnecessary but sufficient
condition). They advocate the view that in a specific situation a
causally relevant condition is a necessary element of a set of
conditions jointly sufficient for the harmful outcome. For this
Wright's term NESS condition (necessary element of a sufficient set) is
currently used, a NESS condition being a specific instance of an INUS
condition. NESS supporters therefore appeal to the idea that particular
causal links are instances of generalisations about the way in which
events are connected. They argue that in order to test whether an
outcome would have occurred in the absence of the agency in question it
is necessary to make a counterfactual calculation, which can only be
done on the basis of such generalisations.

Those who reject the NESS theory either assert that singular causal
judgments do not depend on generalisations or point to the fact that
reliable generalisations of the sort presupposed by it are in practice
virtually confined to inorganic physical processes. Organic processes,
such as those involved in the development of disease, and, still more,
in decision-making by human beings, do not conform to settled patterns.
The NESS theory therefore has at most a narrow range of
application.

Some of those who are impressed by what they see as the deficiencies
of both the but-for and NESS theories prefer a more quantitative or
scalar approach, according to which an agency can cause an outcome to a
greater or less extent (Moore). They argue that an agency must be a
‘substantial factor in’ or ‘contribute to’ the
harmful outcome in order to be legally a cause of it. This approach has
a particular attraction when a number of processes (e.g. several fires
or pollutants) merge to bring about harm. It enables distinctions to be
made according to the extent of contribution of a particular process to
the outcome. It also fits the rule that in most legal contexts an
agency, in order to be responsible for the whole of the harm that
ensues, need only be shown to be one of the causes of harm, not the
sole cause. The criticism that can be made of this approach is that it
presupposes an independent understanding of causes as necessary and/or
sufficient conditions in relation to their consequences.

Difficult legal problems arise in certain cases of
overdetermination, often termed those of ‘overtaking
causes’ or ‘causal preemption’. Suppose that a lethal
dose of poison is given but the victim is fatally wounded before the
poison takes effect. The pre-empting, not the pre-empted condition is
taken to be the cause of the death. Which condition is taken to preempt
the other is sometimes controversial but it is clear than in reaching a
decision attention must be paid to the stages and processes by which
the alleged causes lead to the harmful outcome.

The idea that responsibility should depend on the agent's having
changed the course of events points in the direction of the but-for
theory. The function of cause in relation to recipes and prediction
points towards the NESS theory. The phenomenon of multiple causes,
which have often to be weighed against one another, points to a
quantitative theory. But whichever is favoured has to be applied in the
light the law's commitment to vindicating rights and securing a fair
distribution of risks.

3.2 ‘Proximate cause’

The theories about the specific qualities that an agency must
possess in relation to the outcome in order to be its cause in law are
in Anglo-American law often grouped under this rubric, though many
other terms (e.g. adequate, direct, efficient, operative, legal,
responsible) are also found in the literature. These limiting theories
are invoked because if every causally relevant condition
(cause-in-fact) is treated as grounding responsibility for the outcomes
to which it is causally relevant the extent of legal responsibility
will extend almost indefinitely. (This alarming scenario would however
be subject to independent legal requirements as regards proof, type of
damage and lapse of claims through the passage of time). The theories
in question therefore embody reasons for limiting the extent of legal
responsibility. The reasons adduced for limiting responsibility are
however differently viewed by different theorists. Causal minimalists
treat all these theories as non-causal, in the sense that they embody
grounds of legal policy other than the policy of holding the agent
responsible for the harm caused by their action or intervention. Others
treat some of the suggested limiting factors as causal and others as
non-causal. It is indeed not open to dispute that at least two
non-causal factors limit the extent of legal responsibility. One is the
scope and purpose of the rule of law in question. No rule is intended
to give a remedy for every conceivable type of harm or loss. Another
concerns the aspiration of the law to achieve results that are morally
unobjectionable. This rules out certain claims that would be
inequitable on the part of the claimant or unfair towards the agent. It
needs to be stressed that the grounds for limiting responsibility will
not necessarily be the same in every branch of the law. In particular,
the greater the weight attached to considerations of risk distribution
the more likely it is that different limits will be appropriate in, for
example, criminal, civil and public law.

3.3 Allegedly causal grounds of limitation

Certain theorists reject causal minimalism, which involves a
restricted notion of cause that is current in no extra-legal context.
They propose grounds of limitation that reflect the causal judgements
that would be made outside the law. They claim that these grounds have
a basis in ordinary usage (Hart & Honoré) or in the
metaphysics of causation (Moore). The chief grounds proposed are that
responsibility is limited (i) when a later intervention of a certain
type is a condition of the harmful outcome (ii) when the agency has not
substantially increased the probability of the harmful outcome that in
fact supervenes and (iii) when the causal link involves a series of
steps and ultimately peters out, so that the outcome is too remotely
connected with the alleged cause. They argue that in these cases the
agency, though a causally relevant condition, did not cause the
outcome.

The idea that responsibility is excluded when the harm in question
was conditioned by a later intervention is conventionally
expressed by saying that an intervening or superseding cause broke the
causal link between agency and outcome. These ‘breaks’ are
not conceived as physical discontinuities in the course of events. The
metaphor derives rather from the fact that in an explanatory context a
cause may be regarded as an intervention in the normal course of
events. The most persuasive explanations of an outcome are those that
point to a condition that is abnormal or unexpected in the context or
to a deliberate action designed to bring the outcome about. If these
criteria are then applied in attributive contexts, an agency will not
be regarded as the cause of an outcome when that outcome is explained
by a later abnormal action or conjunction of events or a deliberate
intervention designed to bring it about. A later event of this sort is
contrasted with a state of affairs (e.g .victim's thin skull) existing
at the time of the alleged cause. The latter, however extraordinary,
does not preclude the attribution of the outcome to which it
contributes to the alleged cause. In practice this notion is widely
applied in both civil and, as Kadish has shown, criminal law. The use
of these criteria of intervention in legal systems is said to be
derived from common sense and to be consistent with treating causal
issues in law as questions of fact. It is also supported
(Honoré) on the ground that to attribute only a limited range of
outcomes, whether achievements or failures, to human agents fosters a
sense of personal identity that would be lost if the attribution to
agents was not limited in this way. If there were not such a limiting
factor we should have to share our successes and failures with many
other people of whom it could be said that but for their actions what
we think of as ‘our’ distinctive successes and failures
would not have occurred. For example the success of a student in an
examination would be equally the achievement of all those
(parent, teacher, doctor, grant-giver, girl/boy friend) who made it
possible for the student to succeed. It would not be specially the
student's.

The criticism of this notion of later intervention takes two forms.
First, the criteria set out are too vague to govern decision in
controversial cases. Suppose that a motorist negligently injures a
pedestrian, who is then taken to hospital and wrongly treated for the
injury. Instead of asking whether the mistaken treatment was so
abnormal as not to be accounted a consequence of the motorist's
negligent driving it would, in the critics' eyes, be better to ask
whether the risk of medical mistreatment should be borne exclusively by
the hospital authorities. Secondly, even if the criteria suggested for
selecting certain conditions as causes are in place in explanatory
inquiries they are not necessarily so in attributing responsibility.
There is no good reason to transfer them from an explanatory to an
attributive context. To do so in civil law may result in saddling a
person guilty of momentary carelessness with massive losses
(Waldron).

Another limiting notion that has some claim to be regarded as causal
is that of probability. According to the adequate cause
theory, put forward by the physiologist Von Kries in 1886, developed
systematically by Träger and advocated in a contemporary form by
Calabresi, an agency is a cause only if it significantly increases the
objective probability of the outcome that in fact ensues. Objective
probability is here contrasted with subjective foreseeability, but this
probability must be relative to an assumed epistemic base. It is
inevitably a matter of policy which base to choose, and whether to
include information not known or not available to the agent when he or
she or it acted. Responsibility is excluded in relation to an outcome
the probability of which was not substantially increased by the agency
in question. This theory, long orthodox in German civil law, but
increasingly supplemented by policy-oriented criteria, is intuitively
attractive when the agent wrongfully exposes someone to a risk of harm
to which they would not otherwise be exposed. For example, the agent
wrongfully obstructs a pathway so that the claimant is forced to take a
more dangerous route along a canal, and falls into the canal,
sustaining injury. The obstructer is then the adequate cause of the
injury. But one who wrongfully delays a passenger who is as a result
obliged to board a later airplane, which crashes, is not the adequate
cause of the passenger's death in the crash. At least on the basis of
information available at the time, the probability of being killed in
an air crash was not substantially increased by the delay.

There are however instances in which an agency substantially
increases the probability of harm but the harm that occurs would
intuitively be attributed to a later intervention. Suppose, for
example, that in the example given a passer-by deliberately threw the
claimant into the canal. It would be natural to attribute any injury
suffered by the claimant not to the obstruction of the pathway but to
the act of the third person. This objection can be met by having
recourse to the risk theory, a version of the probability theory with
strong support in Anglo-American writing in both criminal and civil law
(Keeton, Seavey, Glanville Williams). According to this theory
responsibility for harmful outcomes is restricted to the type of harm
the risk of which was increased by the agency's intervention. The harm
must be ‘within the risk’. But much then turns on how the
agent's conduct and the risk are defined. Is the risk of falling into
the canal different from the risk of being pushed into it?

As stated earlier, in law responsibility for harm can rest on risk
allocation as well as on causation. The risk theory has merits that are
independent of its claim to explain what it is for an agency to cause
harm. It can be treated as illustrating a wider principle that
responsibility for harm is confined to the type of harm envisaged by
the purpose of the rule of law violated (Normzweck), a theory espoused
in Germany (Von Cämmerer, J.G.Wolf). For example, if a rule
requiring machinery to be fenced is designed to prevent harmful contact
between the machinery and the bodies of workmen, a workman who suffers
psychological harm from the noise made by the unfenced machine cannot
ground a claim for compensation on the failure to fence. The fencing
requirement was not designed to reduce noise, even though a proper
barrier would have reduced the noise to such an extent as to avoid the
psychological trauma.

The limitations set by the purposes of legal rules cannot be
regarded as causal. They vary from one branch of the law and one legal
system to another. It is true that sometimes the purpose of legal
prohibition may be the simple one of imposing responsibility for the
harm caused by a breach of that prohibition. In that case the limits
set by causal and purposive criteria coincide. But even in such a case
it is a matter of legal policy which types of harm are to be
compensated or to lead to criminal liability. The purposive limits on
responsibility have therefore either to be regarded as additional to
those (later intervention, heightened probability) proposed by those
who reject causal minimalism, or as replacing them. The latter view is
consistent with causal minimalism.

Other proposed criteria of limitation are based on moral
considerations. Theorists who regard fault as an essential condition of
criminal or civil responsibility often argue that a person should not
be liable for unintended and unforeseeable harm. There are problems
about settling whether only the type of harm or the specific harm must
be unforeseeable, and the moment at which foreseeability is to be
judged. But foreseeability, though it bears some relation to
probability, is clearly a non-causal criterion, and one that can apply
only to human conduct, not to other alleged causes. Moreover some
supporters of the risk theory argue that different criteria should
govern the existence and extent of legal liability. Even if the
foreseeability of harm is a condition of liability, sound principles of
risk allocation place on the agent who is at fault in failing to
foresee and take precautions against harm the risk that an
unforeseeable extent of harm will result from his or her fault,
provided that this is of the type that the rule of law in question
seeks to prevent.

There is no reason to suppose that the law, when it engages in
explanatory inquiries, adopts different criteria of causation from
those employed outside the law in the physical and social sciences and
in everyday life. However, even here, requirements of proof may lead to
a divergence, for example, between what would medically be treated as
the cause of a disease and what counts in law as its cause. As regards
attributive uses of cause, the fact that the law has to attend
simultaneously both to the meaning of terms importing causal criteria
and to the purposes of legal rules and their moral status makes the
theory of causation a terrain of debate that is unlikely to yield
solutions commanding general agreement (e.g. Stapleton, Wright 2001;
Moore, forthcoming).